Coordinate input and detection device and information display and input apparatus

ABSTRACT

A coordinate input and detection device includes a touch panel, light emitting units, a reflective member, intensity distribution detection units, a coordinate detection unit, and filters. Each of light beams projected from the light emitting units travels and has a sector shape in a direction parallel to a surface of the touch panel. The light beams are reflected by the reflective member and received by the intensity distribution detection units. A coordinate detection unit detects a coordinate value of a position where the light beams are interrupted based on intensity distributions detected by the intensity distribution detection units. The filters are disposed in optical paths in directions perpendicular to directions in which the light beams travel, and have transmission rates varying with respect to positions within the filters.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to coordinate input anddetection devices and information display and input apparatuses, andmore particularly to a coordinate input and detection device employedin, for instance, an optical coordinate input device, an opticalcoordinate detection device, or an optical touch panel and to aninformation display and input apparatus including such a coordinateinput and detection device and an information display unit having adisplay, such as a large screen display unit with a touch panel, anelectronic blackboard, a video conference apparatus, a large scaleprojection touch panel apparatus, a display-integrated tablet, or amultimedia board.

2. Description of the Related Art

Generally, in conferences or at the presentations of studies, ablackboard or a whiteboard is often employed as an information transfermedium that enables a large number of people to see the content of astudy or proceedings at the same time. Recently, there has been anincreased demand for an electronic blackboard, which can store and printout on papers what is written thereon.

Further, there has been developed an information display and inputsystem that inputs a position or information to a computer in real time,which position or information is indicated or written on a touch panelon a display by a finger of an operator or a touch pen, and displays avariety of information corresponding to the indicated position orwritten information.

In such a system, it is necessary to detect with high accuracy anindicated position, or a touched position, on the surface of the touchpanel when the inputs are made from the touch panel.

For instance, Japanese Patent No. 2678231 discloses, as a coordinateinput and detection device detecting an indicated position on thesurface of a touch panel, a device that has numerous optical emittersand detectors arranged in positions opposing each other on the peripheryof the touch panel surface of a display screen to form a light beammatrix all over the touch panel surface so that a position where lightbeams are interrupted (hereinafter referred to as a light beaminterruption position) by a contact of a finger or a pen with the touchpanel can be detected.

Since the above-mentioned device has an advantage of achieving a highsignal to noise ratio (S/N), the application of the device is extendableto a large-scale display unit. However, since the resolution ofdetection is proportional to a distance between each two adjacentlyarranged optical emitters or detectors, the device requires a largenumber of optical emitters and detectors to be arranged with narrowpitches so as to detect an input coordinate value with high accuracy.Therefore, the signal processing circuit of the optical emitters anddetectors becomes complicated, thus increasing costs.

Japanese Laid-Open Patent Application No. 5-53717 discloses an opticaltwo-dimensional coordinate input device that projects a light beam suchas a laser beam from each of two points outside a touch panel to scan aregion defined by projection angles of each light beam. According to thedevice, the angles of a position of a pen used exclusively for thedevice for retroreflecting the projected light beams are obtained fromthe lights reflected from the pen so as to calculate the coordinateposition of the pen by applying the obtained angles to the principle oftriangulation.

This coordinate input device, however, requires the pen used exclusivelytherefor, thus having an operational problem that an input to the devicecannot be made by means of a finger or any pen other than the pen usedexclusively for the device.

Japanese Laid-Open Patent Application No. 11-85376 discloses a devicethat has a pair of light emitting and receiving units each including alight emitting element, a light receiving element, and a polygon mirrordisposed outside both corners of one side of a display panel. Accordingto the device, the polygon mirrors are turned to scan almost all thesurface of the display panel by means of two light beams. The lightbeams are reflected by retroreflective sheets provided on thelongitudinal sides of the display panel to be detected by the lightreceiving elements of the above-described pair of the light emitting andreceiving units so that a coordinate position is calculated by employingthe principle of triangulation.

This device allows an input by means of a finger or a pen, provides agood visual recognizability, and is relatively easily enlarged in size.However, the device includes mechanical rotating parts, thus generatingnoises and vibrations. Therefore, the device has a difficulty inincreasing detection accuracy in addition to problems of failure anddurability.

The inventor of the present invention has already proposed a coordinateinput and detection device that includes at least a couple of emittingmeans each projecting a light beam that is a parallel beam of anapproximately uniform thickness in a direction perpendicular to a touchpanel and has a sector shape in a direction parallel to the touch panel.According to the device, the light beams travel over a given region ofthe touch panel almost parallel to the surface thereof to be reflectedby retroreflective sheets provided on the peripheral portion of thetouch panel. The reflected lights are detected by at least a couple ofintensity distribution detection means, which are optical-electricaltransducers such as charge coupled devices (CCDs), so that the intensitydistribution of each light is detected. The coordinate value of aposition where the lights beams traveling over the given region of thetouch panel are interrupted is detected by the intensity distributionsof the light beams.

According to the above-described device, by interrupting a part of eachlight beam projected all over the given region of the touch panel byindicating a position on the surface of the touch panel by means of anyindicator such as a finger or a pen, the coordinate value of the lightbeam interruption position is detected with high accuracy so that adesired input operation is performed. Therefore, the device dispenseswith a special pen including a reflective material. Further, since thedevice does not employ a mechanical scanning mechanism such as a polygonmirror, the device is free of noises and vibrations to achieve gooddetection accuracy with fewer failures and good durability, thuseliminating all of the conventional disadvantages.

However, in order to detect the light beam interruption position withgood accuracy from the intensity distributions of the light beamsreceived by the intensity distribution detection means, each of thelight beams received by the light receiving surfaces of theabove-described intensity distribution detection means is required tohave its amount of light approximately uniformly distributed in adirection parallel to the surface of the touch panel and perpendicularto a traveling direction of the reflected light of the light beamtraveling over the given region of the touch panel.

However, the distribution of the amount of light in a directionperpendicular to the optical axis of a light-emitting diode (LED) or alaser diode (LD) employed as a light source of each light emittingmeans, which distribution correlates to the intensity distribution oflight emission, has a non-uniform characteristic that as indicated by acurve 51 shown in FIG. 1, the amount of light is maximized around alight source 50 and decreases in proportion to a distance therefrom.

Therefore, in the case of forming, by a combination of cylindricallenses, the light beam into the parallel beam of the approximatelyuniform thickness in the direction perpendicular to the touch panel andinto the sector shape in the direction parallel to the touch panel, thedistribution of the amount of light in the direction parallel to thesurface of the touch panel particularly has a characteristic that theamount of light is maximized at the center portion of the light beam anddecreases as a measurement point of the amount of light approaches eachend portion of the light beam.

Therefore, a light modulation plate 60 is disposed on an optical path ofthe light beam projected from each light emitting means to be receivedby each intensity distribution detection unit 70 so that the amount oflight is modulated to be uniformly distributed in the direction parallelto the surface of the touch panel.

That is, as shown in FIG. 1, a light beam 55 projected from each lightemitting means (not shown) to be reflected back from the retroreflectivesheet is made incident on a condenser lens (image formation lens) 71 ofthe intensity distribution detection unit 70 through an opening portion60 a of the light modulation plate 60. An image is formed, by thefunction of the condenser lens 71, on a light receiving element array 72b formed by light receiving elements arranged in a linear array on alight receiving surface 72 a of a CCD 72 that is an optical-electricaltransducer so that the intensity distribution of the light beam 55 isdetected.

The light modulation plate 60 is stamped out from a sheet metal to haveits outer shape and the opening portion 60 a formed. The opening portion60 a is a slit longitudinally narrow in a spreading direction of thelight beam 55 parallel to the surface of the touch panel (in aright-to-left direction or a Y-axial direction in FIG. 1), and has itswidth d gradually varying so as to be the widest at both end portionsthereof and the narrowest at the center thereof.

Therefore, if a light beam having its amount of light distributeduniformly all over the opening portion 60 a in a longitudinal directionthereof is made incident on the opening portion 60 a, the amount oflight of the light beam passing through the light modulation plate 60 isdistributed to be minimized at the center portion of the light beam andmaximized at both end portions thereof, as indicated by a curve 52 shownin FIG. 1.

However, as described above, the distribution of the amount of light ofthe actual light source 50 has the characteristic indicated by the curve51 of FIG. 1. Therefore, by passing through the light modulation plate60, the light beam can be modulated to have its amount of lightdistributed almost uniformly in the Y-axial direction as indicated by abroken curve 53 of FIG. 1.

The light beam 55 is made incident on the condenser lens 71 so as to begathered at the center thereof in the Y-axial direction, and islaterally reversed to form the image on the light receiving elementarray 72 b of the CCD 72 so that the intensity distribution of the lightbeam is detected. Accordingly, in this manner, an intensity distributionsignal having an almost uniform level all over the light receivingelement array 72 b is usually detected.

Thus, by changing the shape of the opening portion 60 a of the lightmodulation plate 60, the incident light beam can be modulated to have adesired distribution of its amount of light. Therefore, the distributionof the amount of light of the light beam 55 in the Y-axial direction canbe adjusted to the characteristic of the CCD 72.

This requires a thickness D of the incident light beam 55 in a directionperpendicular to the surface of the touch panel to be thicker than acertain thickness, and the maximum value of the width d of the openingportion 60 a of the light modulation plate 60 is determined based on thethickness D. If the maximum value of the width d is small, a variationin the width d is prevented from being great, thus narrowing a lightmodulation range. Therefore, the narrowed light modulation range,together with a limit to the dimensions of a metal mold for processingthe sheet metal and a problem of processing accuracy, prevents a desiredlight modulation characteristic from being obtained.

However, in the above-described coordinate input and detection device,the thickness D of the sector-shaped light beam 55 projected over thesurface of the touch panel is required to be as thin as possible tominimize a detectable region in the direction perpendicular to thesurface of the touch panel so that a wrong detection based on anunnecessary interruption of the light beam other than an indication bymeans of a finger or an indication pen is prevented from being causedand that the detection accuracy of the coordinate value of a light beaminterruption position is increased.

It is difficult to satisfy both of the above-described requirements. Theabove-described adjustment of the distribution of the amount of light ofthe light beam 55 incident on the light receiving surface 72 a by meansof the light modulation plate 60 is prevented from making sufficientlythin the thickness D of the light beam 55 in the direction perpendicularto the surface of the touch panel. Therefore, there remains the problemthat a wrong detection based on an unnecessary interruption of the lightbeam other than an indication by means of a finger or an indication penis caused or a sufficient detection accuracy of the coordinate value ofa light beam interruption position is prevented from being obtained.

SUMMARY OF THE INVENTION

It is a general object of the present invention to provide a coordinateinput and detection device and an information display and inputapparatus in which the above-described disadvantages are eliminated.

A more specific object of the present invention is to provide acoordinate input and detection device which makes each of sector-shapedlight beams projected over the surface of a touch panel as thin aspossible in a direction perpendicular to the surface of the touch panelso that a wrong detection based on an unnecessary interruption of eachlight beam other than an indication by means of a finger or anindication pen is prevented from being caused and that the detectionaccuracy of the coordinate value of a light beam interruption positionis increased, and adjusts each light beam made incident on each lightreceiving surface so that each light beam is distributed uniformly in aspreading direction thereof parallel to the surface of the touch panelalso for the purpose of increasing the detection accuracy.

It is another more specific object of the present invention to providean information display and input apparatus including such a coordinateinput and detection device.

The above objects of the present invention are achieved by a coordinateinput and detection device including: a touch panel including a surface;a plurality of light emitting units projecting light beams travelingparallel to the surface of the touch panel over a predetermined regionof the touch panel, each of the light beams being a parallel beam havinga uniform thickness in a direction perpendicular to the surface of thetouch panel and having a sector shape in a direction parallel to thesurface of the touch panel; a reflective member provided on a peripheralportion of the touch panel to reflect the light beams toward firstoptical paths through which the respective light beams travel to reachthe reflective member; a plurality of intensity distribution detectionunits receiving the respective light beams reflected by the reflectivemember to detect intensity distributions of the light beams; acoordinate detection unit detecting a coordinate value of a positionwhere the light beams are interrupted based on the intensitydistributions; and a plurality of filters disposed in respective secondoptical paths in directions perpendicular to directions in which therespective lights beams travel, the second optical paths being opticalpaths through which the respective light beams reflected by thereflective member travel to reach the respective intensity distributiondetection units, the filters having transmission rates varying withrespect to positions within the filters.

According to the above-described coordinate input and detection device,the distribution of the amount of light of each light beam can beadjusted to have an optimum characteristic by varying the transmissionrate of each filter along a longitudinal length thereof even though athickness of each light beam passing through each filter is thin.

Therefore, a wrong detection based on an unnecessary interruption ofeach light beam other than an indication by means of a finger or anindication pen or based on non-uniformity of the distribution of amountof light is prevented from being caused, and an input position detectionwith higher accuracy and increased reliability can be performed.

The above objects of the present invention are also achieved by aninformation display and input apparatus including an information displayunit including a display for displaying a variety of information, and acoordinate input and detection device, which device includes: a touchpanel including a surface, the touch panel serving as the display of theinformation display unit; a plurality of light emitting units projectinglight beams traveling parallel to the surface of the touch panel over apredetermined region of the touch panel, each of the light beams being aparallel beam having a uniform thickness in a direction perpendicular tothe surface of the touch panel and having a sector shape in a directionparallel to the surface of the touch panel; a reflective member providedon a peripheral portion of the touch panel to reflect the light beamstoward first optical paths through which the respective light beamstravel to reach the reflective member; a plurality of intensitydistribution detection units receiving the respective light beamsreflected by the reflective member to detect intensity distributions ofthe light beams; a coordinate detection unit detecting a coordinatevalue of a position where the light beams are interrupted based on theintensity distributions; and a plurality of filters disposed inrespective second optical paths in directions perpendicular todirections in which the respective lights beams travel, the secondoptical paths being optical paths -through which the respective lightbeams reflected by the reflective member travel to reach the respectiveintensity distribution detection units, the filters having transmissionrates varying with respect to positions within the filters.

The above objects of the present invention are further achieved by aninformation display and input apparatus including an information displayunit including a display for displaying a variety of information, and acoordinate input and detection device, which device includes: a touchpanel including a surface, the touch panel being made of a transparentmaterial and placed on the display of the information display unit; aplurality of light emitting units projecting light beams travelingparallel to the surface of the touch panel over a predetermined regionof the touch panel, each of the light beams being a parallel beam havinga uniform thickness in a direction perpendicular to the surface of thetouch panel and having a sector shape in a direction parallel to thesurface of the touch panel; a reflective member provided on a peripheralportion of the touch panel to reflect the light beams toward firstoptical paths through which the respective light beams travel to reachthe reflective member; a plurality of intensity distribution detectionunits receiving the respective light beams reflected by the reflectivemember to detect intensity distributions of the light beams; acoordinate detection unit detecting a coordinate value of a positionwhere the light beams are interrupted based on the intensitydistributions; and a plurality of filters disposed in respective secondoptical paths in directions perpendicular to directions in which therespective lights beams travel, the second optical paths being opticalpaths through which the respective light beams reflected by thereflective member travel to reach the respective intensity distributiondetection units, the filters having transmission rates varying withrespect to positions within the filters.

According to the above-described information display and inputapparatuses, the same effects as those of the above-described coordinateinput and detection device can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome more apparent from the following detailed description when readin conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram for illustrating a means for adjusting adistribution of amount of light of a received light beam in an opticalunit of a conventional information display and input apparatus;

FIG. 2 is a diagram showing a structure of an optical unit of anembodiment of a coordinate input and detection device according to thepresent invention and optical paths of projected and reflected lightbeams in the optical unit;

FIG. 3 is a schematic diagram of an overall structure of the coordinateinput and detection device of FIG. 2;

FIG. 4 is a diagram for illustrating a detection region on a touch panelcovered by a pair of optical units shown in FIG. 3;

FIG. 5 is a block diagram showing a structure of an operation parttogether with the optical units shown in FIG. 3;

FIG. 6 is a block diagram showing only a portion of the operation partshown in FIG. 5, which portion is used so that a CPU performs acoordinate detection operation;

FIG. 7 is a diagram for illustrating a peak point detected by a peakdetector shown in FIG. 6;

FIG. 8 is a diagram for illustrating an operation performed by an x-ycomputing element shown in FIG. 6 for computing a coordinate value of aposition where light beams are interrupted;

FIG. 9 is a diagram showing a structure and a characteristic of a firstembodiment of a filter employed as a means for adjusting a distributionof amount of light in the coordinate input and detection deviceaccording to the present invention;

FIGS. 10A through 10C are diagrams showing a structure of a secondembodiment of the filter according to the present invention;

FIG. 11 is a diagram for illustrating a characteristic of the filtershown in FIGS. 10A through 10C;

FIGS. 12A and 12B are diagrams for illustrating a state where adhesionportions are provided on first and second filters forming the filtershown in FIGS. 10A through 10C;

FIG. 13 is a plan view of an attachment frame to which the first andsecond filters shown in FIGS. 12A and 12B are affixed;

FIG. 14 is a diagram showing a structure and a characteristic of a thirdembodiment of the filter according to the present invention; and

FIG. 15 is a perspective view of an embodiment of an information displayand input apparatus according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will now be given, with reference to the accompanyingdrawings, of embodiments of the present invention.

FIG. 2 is a diagram showing a structure of an optical unit of anembodiment of a coordinate input and detection device according to thepresent invention and optical paths of projected and reflected lightbeams in the optical unit. FIG. 3 is a schematic diagram of an overallstructure of the coordinate input and detection device. FIG. 4 is adiagram for illustrating a detection region on a touch panel 10 coveredby a pair of the optical units 1L and 1R.

According to FIG. 3, the coordinate input and detection device includesthe touch panel 10 and a pair of the optical units 1L and 1R eachprovided slantwise on a corresponding corner portion of the bottom sideof the touch panel 10. Each of the optical units 1L and 1R includes anoptical system including a light source 3, a CCD 13, a half mirror 11,cylindrical lenses 9 a through 9 c, a condenser lens (image formationlens) 12, and a filter 4; The light source 3 and the cylindrical lenses9 a through 9 c form a light emitting part 6, and the CCD 13 and thecondenser lens 12 form a light receiving part 7.

A retroreflective sheet 2 that is a reflective member is provided on thethree sides other than the bottom side of the touch panel 10. Theretroreflective sheet 2, which is, for instance, an arrangement ofnumerous cylindrical corner cubes, has the characteristic of reflectingan incident light to the same optical path.

The retroreflective sheet 2 is provided on the three sides other thanthe bottom side of the touch panel 10 and the optical units 1L and 1Rare provided on the left and right corners of the bottom side of thetouch panel 10, respectively, because the reflection efficiency of theretroreflective sheet 2 may be deteriorated by dust prone to collectthereon if the retroreflective sheet 2 is disposed on the bottom side ofthe touch panel 10.

As shown in FIG. 4, light beams projected from the optical units 1L and1R spread out in sector shapes covering regions within angles θA and θB,respectively, in a direction parallel to a panel surface 10 a of thetouch panel 10 so that a position can be detected in almost all theregion of the panel surface 10 a. As the angles θA and θB becomegreater, the sector-shaped light beams cover a greater region of thepanel surface 10 a, so that an extensive position detection isperformable.

Each of the light beams projected from the optical units 1L and 1R is aparallel beam having a uniform thickness in a direction perpendicular tothe panel surface 10 a.

In FIG. 3, for convenience of description, the sector-shaped light beamprojected from the optical unit 1L is formed of a bundle of lights L1through Lm, and similarly, the sector-shaped light beam projected fromthe optical unit 1R is formed of a bundle of lights R1 through Rm.

The light beams projected from the optical units 1L and 1R travelparallel to the panel surface 10 a of the touch panel 10 to reach theretroreflective sheet 2 provided on the three sides of the touch panel10. Upon reaching the retroreflective sheet 2, the respective lightbeams are reflected back therefrom to the optical units 1L and 1Rthrough the same optical paths as indicated by reflected lights L2′ andR2′ in FIG. 3.

However, if an interrupting object such as an indicator P exists on thepanel surface 10 a, projected lights hitting the interrupting object areinterrupted thereby and do not reach the retroreflective sheet 2.Therefore, the projected lights are never reflected back from theretroreflective sheet 2 to the respective optical units 1L and 1R.

Directions from which the projected lights are not reflected back can bedetected from detection signals generated by the light receiving parts 7in the respective optical units 1L and 1R. Based on the detectionsignals generated by the light receiving parts 7 in the respectiveoptical units 1L and 1R, an operation part 20 that is a coordinatedetection unit performs an operation to detect the coordinate value of aposition where the lights traveling over a given region of the touchpanel 10 are interrupted by the indicator P. The details of thisoperation will be described later.

The coordinate data of the position detected by the operation part 20 isoutputted to a computer 14 through an interface part 26.

Next, a detailed description will be given of the structures of theoptical units 1L and 1R, and the optical paths of the projected lightbeams and the light beams reflected back from the retroreflective sheet2.

Since the optical units 1L and 1R have the same structure, a descriptionof the optical unit with reference to FIG. 2 applies to both opticalunits 1L and 1R.

In FIG. 2, coordinate axes of directions parallel to the panel surface10 a of the touch panel 10 are defined as an X-axis and a Y-axis,respectively, and a coordinate axis of a direction perpendicular to thepanel surface 10 a is defined as a Z-axis.

Each of the optical units 1L and 1R includes the light emitting part 6,which is a light emitting unit, the light receiving part 7, which is anintensity distribution detection unit, the half mirror 11, which is alight splitting member, and the filter 4, which is a unit for adjustingthe distribution of amount of light.

FIG. 2 is basically a view from an X-Z plane. However, a part framed bya double dot chain line a, which is a diagram viewing the light emittingpart 6 in a direction indicated by arrow A from an X-Y plane, and a partframed by a double dot chain line b, which is a diagram viewing thelight receiving part 7 in a direction indicated by arrow B-from an Y-Zplane, are also shown in FIG. 2 for convenience of graphicalrepresentation.

The light emitting part 6 includes the light source 3 whose spot can benarrowed to some extent, such as an LD or an LED. The light beamprojected from the light source 3 is collimated by the cylindrical lens9 a, which functions as a convex lens only in a Z-axial direction, to bea thin parallel beam having a uniform thickness in the directionperpendicular to the panel surface 10 a (in the Z-axial direction).Then, the light beam is diffused in the sector shape in the directionparallel to the panel surface 10 a (in the Y-axial direction) by the twocylindrical lenses 9 b and 9 c each functioning as a concave lens onlyin the Y-axial direction.

Thus, the light beam that is the thin parallel beam having the uniformthickness in the direction perpendicular to the panel surface 10 a andis diffused, in the direction parallel to the panel surface 10 a, in thesector shape having a predetermined angle from the position where thelight emitting part 6 is disposed is projected almost parallel to thepanel surface 10 from the light emitting part 6. The projected lightbeam passes through the half mirror 11 to be radiated almost all overthe detection region of the panel surface 10 a.

If not interrupted on the way, the light beam reaches theretroreflective sheet 2 provided on the periphery of the touch panel 10to be retroreflected therefrom. The reflected light beam returns to thesame optical unit through the same optical path, and is reflected by 90°from the half mirror 11 to be made incident on the light receiving part7 through the filter 4.

The filter 4 is disposed in a direction perpendicular to a travelingdirection of the reflected light beam. The transmission rate of thefilter 4 differs along its length in the direction in which the filter 4is disposed, especially, in the direction in which the light beamspreads out (in the Y-axial direction) shown in the part framed by thedouble dot chain line b in FIG. 2, so that the amount of light isadjusted to be distributed uniformly in that direction. A detaileddescription of the filter 4 will be given later.

The light receiving part 7 includes the condenser lens (image formationlens) 12 that is a convex lens and the CCD 13 that is anoptical-electrical transducer. The reflected light beam is propagated inthe direction lateral to the panel surface 10 a to concentrate at thecenter of the condenser lens 12, and in the direction perpendicular tothe panel surface 10 a to be made incident on the condenser lens 12 inthe same form of the parallel beam. Therefore, due to the function ofthe condenser lens 12, the reflected light beam is formed on a lightreceiving surface 13 a of the CCD 13 disposed on the focal surface ofthe condenser lens 12 into the image of a thin line parallel to theY-axial direction, which line corresponds to a linear array arrangementof light receiving elements.

Thereby, the intensity distribution of the light beam parallel to theY-axial direction is formed on the light receiving surface 13 a of theCCD 13 depending on the presence or absence of retroreflected lights,and is detected by the CCD 13 to be converted into an electrical signal.That is, if the retroreflected light beam is interrupted by a finger ora pen, a point of weak optical intensity, which is a later-describedpeak point, is generated in a position corresponding to an interruptedretroreflected light on the light receiving surface 13 a, and appears inthe waveform of the detection signal.

Next, a description will be given of the operation part 20 shown in FIG.3. FIG. 5 is a block diagram showing a structure of the operation part20 together with the optical units 1L and 1R.

The operation part 20 includes a CPU 21 supervising and controlling thewhole part, a ROM 22 storing fixed data such as control programs of theCPU 21, a RAM 23 storing temporary data, a timer 24 controlling the timeintervals of light emission from the light source 3 provided in each ofthe optical units 1L and 1R, peak detectors 25L and 25R, an x-ycomputing element 29, and a bus 27 connecting the above-described parts.The RAM 23 includes the regions of waveform memories 28L and 28R. Theoperation part 20 is connected to the computer 14 via the interface part26.

The operation part 20 performs the operation to detect the coordinatevalue of a position where the light beam traveling over the panelsurface 10 a is interrupted based on an electrical signal inputted fromeach of the CCDs 13 of the optical units 1L and 1R, which signalcorresponds to the intensity distribution of the retroreflective lightbeam in the direction parallel to the panel surface 10 a.

A description will be given, with reference to FIGS. 6 through 8, of theabove-mentioned operation. FIG. 6 is a block diagram showing only aportion of the operation part 20, which portion is used so that the CPU21 performs the coordinate detection operation.

First and second waveform data representing the intensity distributionsof the light beams in the direction parallel to the panel surface 10 a,which intensity distributions are outputted as electrical signals fromthe respective CCDs 13 of the optical units 1L and 1R shown in FIG. 3,are inputted to the operation part 20. Hereinafter, the CCDs 13 of theoptical units 1L and 1R are referred to as a CCD 13L and a CCD 13R,respectively. The first and second waveform data are then stored in thewaveform memories 28L and 28R in the RAM 23 shown in FIG. 5,respectively. The peak detectors 25L and 25R perform operations todetect the positions of the peak points of the first and second waveformdata stored in the waveform memories 25L and 25R, respectively.

FIG. 7 is a diagram for illustrating a peak point. For instance, if thesector-shaped light beam formed of the lights L1, L2, L3, . . . , Ln−1,Ln, . . . , . . . , and Lm projected from the optical unit 1L has thenth light Ln interrupted by the indicator P such as a finger or a pen,the nth light Ln never reaches the retroreflective sheet 2. Therefore,since the nth light Ln is never detected by the CCD 13L of the opticalunit 1L, a point of weak optical intensity (dark point) is generated ina position in the optical detector array of the CCD 13L at a distanceDnL from a center C thereof. Hereinafter, this position is referred toas a position DnL. As a result, a peak point of a lowered level appearsin the waveform of the intensity distribution of the light beamoutputted from the CCD 13L. Similarly, with respect to the optical unit1R, a dark point is generated in a position DnR in the optical detectorarray of the CCD 13R, and consequently, a peak point of a lowered levelappears in the waveform of the intensity distribution of the light beamoutputted from the CCD 13R.

The peak detectors 25L and 25R detect the positions DnL and DnR of thedark points that are the peak points of the waveforms, respectively, bymeans of, for instance, a waveform calculation method such as smoothingdifferential.

When the positions of the peak points are detected from the first andsecond waveform data by the peak detectors 25L and 25R, respectively,the x-y computing element -29 computes the coordinate value (x, y) ofthe position of the indicator P that causes the peak points to appear inthe first and second waveform data.

A description will be given, with reference to FIG. 8, of an operationof the x-y computing element 29 for computing the coordinate value (x,y) of the position of the indicator P.

An angle of projection or incidence θ nL of the light Ln of the opticalunit 1L interrupted by the indicator P shown in FIG. 7, together with anangle of projection or incidence θ nR of the light Rn of the opticalunit 1R, can be computed from the following formulas.

θnL=arctan (DnL/f)  (1)

θnR=arctan (DnR/f)  (2)

In the above-mentioned formulas, DnL is the position of the dark pointon the CCD 13L of the optical unit 1L detected by the peak detector 25L,DnR is the position of the dark point on the CCD 13R of the optical unit1R detected by the peak detector 25R, and f is a distance between thecondenser lens 12 and the light receiving elements of each of the CCDs13L and 13R, which distance corresponds to the focal length of thecondenser lens 12.

By employing θ nL obtained from the formula (1) and θ nR obtained fromthe formula (2), an angle θL formed between the light Ln of the opticalunit 1L shown in FIG. 8 and the bottom side (X-axial) of the touch panel10, and an angle θ R formed between the light Rn of the optical unit 1Rand the bottom side (X-axial) of the touch panel 10 can be computed fromthe following formulas.

θL=g(θnL)  (3)

θR=h(θnR)  (4)

In the above-mentioned formulas, g is a deformation coefficient of thegeometric relative positional relation between the touch panel 10 andthe optical unit 1L, and h is a deformation coefficient of the geometricrelative positional relation between the touch panel 10 and the opticalunit 1R.

The coordinate value (x, y) of the position where the lights beams areinterrupted by the indicator P is computed from the following formulasunder the principle of triangulation.

x=w tan θR/(tan θL+tan θR)  (5)

y=w tan θL tan θR/(tan θL+tan θR)  (6)

In the above-mentioned formulas, w is a distance between the opticalunits 1L and 1R.

Thus, the coordinate value (x, y) of the position where the lights Lnand Rn are interrupted by the indicator P is computed from thecalculations of the formulas (1) through (6) by detecting the positionsDnL and DnR. Programs required for the above-described calculations canbe prestored in the ROM 22 as parts of the operation program of the CPU21.

Here, a description will be given collectively of an overall operationof the coordinate input and detection device having the above-describedstructure.

As shown in FIG. 8, if a point on the panel surface 10 a of the touchpanel 10 of the coordinate input and detection device is indicated bythe indicator P such as a finger or a pen, the lights Ln and Rnprojected respectively from the optical units 1L and 1R are interruptedby the indicator P so as to be prevented from reaching theretroreflective sheet 2. Therefore, the lights Ln- and Rn are neverdetected by the CCDs 13L and 13R of the optical units 1L and 1R,respectively.

Thereby, the points of weak optical intensity (dark points) aregenerated in the positions DnL and DnR on the respective CCDs 13L and13R, and the first and second waveform data corresponding to theintensity distributions of the reflected lights in the directionparallel to the panel surface 10 a are stored in the waveform memories28L and 28R, respectively. Based on the first and second waveform data,the peak detectors 25L and 25R detect the positions DnL and DnR of thedark points on the respective CCDs 13L and 13R, and the x-y computingelement 29 computes the coordinate value (x, y) of the position wherethe lights Ln and Rn are interrupted. Data of thus obtained coordinatevalue (x, y) is inputted to the computer 14 via the interface part 26,and an operation corresponding to the indicated position is performed.

Next, a description will be given of the filter 4 provided in theoptical unit shown in FIG. 2, which filter is the most important elementof the present invention.

In the above-described coordinate input and detection device accordingto the present invention, in order to increase the detection accuracy ofthe coordinate value of an input position, it is required, at least, tomake as thin as possible the thickness of each of the sector-shapedlight beams projected parallel to the panel surface 10 a of the touchpanel 10 from the optical units 1L and 1R, respectively, and to have theamount of light of each light beam distributed uniformly in thedirection in which the light beam spreads out in the sector shape.However, as previously described, since the amount of light of the lightbeam projected from the light source 3 shown in FIG. 1 is large in thecenter portion of the light beam spreading in the sector shape anddecreases as the measurement point of the amount of light approacheseach side of the light beam. Therefore, the filter 4 is employed tocorrect the distribution of the amount of light of the light beam.

FIG. 9 is a diagram showing a shape and a characteristic of a firstembodiment of the filter 4.

The filter 4 is formed of a single long thin resin film whose opticaltransmission rate is 25%, and, as shown in FIG. 2, is disposed, in theoptical path of the light beam made incident on the light receiving part7, in the direction perpendicular to the traveling direction of thelight beam so that the light beam spread out in a longitudinal directionof the filter 4. The filter 4 has wedge-like notches 4 b protruding fromthe respective longitudinal end portions toward the center portionthereof.

Therefore, although a portion a of the filter 4 without any notches 4 bhas a transmission rate of 25%, the transmission rate of each portion bincluding the notch 4 b increases as a measurement point of thetransmission rate approaches each longitudinal end portion of the filter4 so as to reach almost 100% at each side thereof.

Thus, if a light beam is made incident on the filter 4 so that itsamount of light is distributed uniformly all over the filter 4, thelight beam passing through the filter 4 has its amount of lightdistributed in the Y-axial direction with a characteristic indicated bya curve 31 in FIG. 9.

However, an actual light beam made incident on the filter 4 does nothave its amount of light distributed uniformly in the Y-axial direction,and therefore, the distribution of the amount of light has acharacteristic indicated by the curve 51 in FIG. 9 as in theconventional example described with reference to FIG. 1. Therefore, ifthe light beam having such a distribution of the amount of light passesthrough the filter 4 of this embodiment, due to the transmission ratedistribution of the filter 4, the distribution of the amount of light isaveraged as indicated by a broken curve 32 in FIG. 9 to be almostuniform in the Y-axial direction.

Next, a description will be given, with reference to FIGS. 10A through13, of a second embodiment of the filter 4.

In this embodiment, as shown in FIGS. 10A and 10B, first and secondfilters 41 and 42 having different shapes and optical transmission ratesare superposed on each other to form the filter 4 shown in FIG. 10C.

The first filter 41 of FIG. 10A has an optical transmission rate of 25%,and includes deep wedge-like notches 41 a protruding from the respectivelongitudinal end portions toward the center portion thereof. On theother hand, the second filter 42 of FIG. 10B has an optical transmissionrate of 50%, and includes shallow wedge-like notches 42 a protrudingfrom the respective longitudinal end portions toward the center portionthereof.

FIG. 10C shows a state in which the filter 4 is formed by superposingthe first and second filters 41 and 42.

Therefore, the transmission rate of a portion 4 a of the filter 4 wherethe first and second filters 41 and 42 are superposed is 12.5%(25%×50%=12.5%), the transmission rate of each portion 4 b formed onlyof the first filter 41 is 25%, the transmission rate of each portion 4 cformed only of the second filter 42 is 50%, and the transmission rate ofeach portion 4 d formed only of the notches is 100%.

Thus, if a light beam is made incident on the filter 4 so that itsamount of light is distributed uniformly all over the filter 4, thelight beam passing through the filter 4 has its amount of lightdistributed in the Y-axial direction with a characteristic indicated bya curve 33 in FIG. 11.

However, an actual light beam made incident on the filter 4 does nothave its amount of light distributed uniformly in the Y-axial direction,and therefore, the distribution of the amount of light has thecharacteristic indicated by the curve 51 in FIG. 11 as in theconventional example described with reference to FIG. 1. Therefore, ifthe light beam having such a distribution of the amount of light passesthrough the filter 4 of this embodiment, due to the transmission ratedistribution of the filter 4, the distribution of the amount of light isaveraged as indicated by a broken curve 34 in FIG. 11 to be almostuniform in the Y-axial direction.

Thus, by a combination of a plurality of filters having differentoptical transmission rates and notch shapes, a filter having a desiredtransmission rate distribution can be made with more ease.

In order to attach the filter 4 to a predetermined position in each ofthe optical units 1L and 1R, as shown in FIGS. 12A and 12B, an adhesionportion 41 c is provided on each longitudinal side portion of the firstfilter 41 and an adhesion portion 42 c is provided on each longitudinalside portion of the second filter 42 so that the first and secondfilters 41 and 42 are superposed to be affixed to an attachment frame 45made of a sheet metal shown in FIG. 13.

The attachment frame 45 has formed therein a rectangular window 45 a forrestricting the transmission region of the light beam and a pair ofholes 45 b through which pass screws for attaching the attachment frame45 to a support member of each of the optical units 1L and 1R.

Therefore, by inserting the screws into a pair of the holes 45 b, theattachment frame 45 to which the filter 4 is affixed can be fixed to thesupport member of each of the optical units 1L and 1R.

As the adhesion portion 41 c or 42 c, a double-sided tape or an adhesiveagent can be employed. It is preferable that each of the adhesionportions 41 c and 42 c be made as thin and narrow as possible. Further,the first and second filters 41 and 42 are required to be affixed orfixed so that the incident light beam is precluded from passing througheach of the adhesion portions 41 c and 42 c to prevent the transmissionrate of the filter 4 from becoming inaccurate.

Next, a description will be given, with reference to FIG. 14, of a thirdembodiment of the filter 4.

The filter 4 of this embodiment is a combination of three filters 46through 48 having different optical transmission rates and longitudinallengths. The filters 46 through 48 include wedge-like notches 46 a, 47a, and 48 a of the same depth protruding from each longitudinal endportion toward each center portion thereof.

The longest filter 46 has a transmission rate of 25%, the second longestfilter 47, whose longitudinal ends are indicated by one dot chain lines,has a transmission rate of 50%, and the shortest filter 48, whoselongitudinal ends are indicated by broken lines, has a transmission rateof 75%. The transmission rate of the filter 4 varies slightly along thelength thereof, so that a variation in the transmission rate becomessmoother.

Thus, if a light beam is made incident on the filter 4 so that itsamount of light is distributed uniformly all over the filter 4, thelight beam passing through the filter 4 has its amount of lightdistributed in the Y-axial direction with a characteristic indicated bya curve 35 in FIG. 14.

However, an actual light beam made incident on the filter 4 does nothave its amount of light distributed uniformly in the Y-axial direction,and therefore, the distribution of the amount of light has thecharacteristic indicated by the curve 51 in FIG. 14 as in theconventional example described with reference to FIG. 1. Therefore, ifthe light beam having such a distribution of the amount of light passesthrough the filter 4 of this embodiment, due to the transmission ratedistribution of the filter 4, the distribution of the amount of light isaveraged as indicated by a broken curve 36 in FIG. 14 to be almostuniform in the Y-axial direction.

The optical transmission rates of the three filters 46 through 48 can beset so as to correct not only the distribution of the amount of light ofthe incident light beam but also a characteristic of the condenser lens12 shown in FIG. 2 or a sensitivity characteristic of each of the CCDs13L and 13R. The same transmission rate may be employed by the three ortwo of the filters 46 through 48, or the three filters 46 through 48 mayhave different transmission rates as described above. Each transmissionrate can be selected freely from the range of more than 0% to less than100%.

Further, the number of employed filters and the transmission rate,shape, and material (resin film, glass, plastic, etc.) of each employedfilter can be freely combined so that a desired characteristic can beobtained.

The filter 4 may be disposed in any position in each of the opticalpaths through which the light beams projected from the light emittingparts 6 of the optical units 1L and 1R are reflected back from theretroreflective sheet 2 to be received by the respective light receivingparts 7. However, the closer the filter 4 is disposed to the lightreceiving surface 13 a of each of the CCDs 13L and 13R of the lightreceiving parts 7, the smaller the longitudinal dimension of the filter4 can be made. Further, the filter 4 may be provided on the side of eachof the light emitting parts 6.

Finally, a description will be given, with reference to FIG. 15, of anembodiment of an information display and input apparatus including thecoordinate input and detection device according to the presentinvention.

FIG. 15 is a perspective front-side view of a multimedia board that isthe information display and input apparatus.

The multimedia board 80 includes a board part 81, which is used as alarge screen display for displaying a variety of information and also asa touch panel of the above-described coordinate input and detectiondevice, a computer housing part 83 provided on a caster board 82, avideo deck housing part 84 provided on the computer housing part 83, anda printer housing part 85 provided on the video deck housing part 84.The board part 81 is supported by a pillar provided on its backside tobe provided on the printer housing part 85. The upper surface of theprinter housing part 85 is also used as a keyboard stand 86 for placinga keyboard (not shown) thereon.

The board part 81 includes a plasma color display that is an informationdisplay unit employing a large screen flat panel 81 a, and theabove-described coordinate input and detection device incorporated intothe plasma color display. The flat panel 81 a is also used as theabove-described touch panel 10, and the above-described pair of theoptical units 1L and 1R are housed inside the left and right cornerportions of the lower portion of a frame body 81 b of the board part 81,respectively. The retroreflective sheet 2 is provided on the peripheryof the flat panel 81 a except for the bottom side thereof.

A drive unit of the plasma color display and a controller unit of thecoordinate input and detection device, which unit includes the operationpart 20 shown in FIG. 3, are provided on the backside of the board part81.

According to the multimedia board 80, when information is freely writtento or an indication is freely provided on the screen of -the flat panel81 a by means of a finger or a pen, the as-written information orinformation corresponding to the indication can be displayed on theprojector-like large screen of the board part 81, and the information orthe indication can be inputted to a computer housed in the computerhousing part 83. Further, a sharp color image based on data from thecomputer or reproduced image data from a video deck housed in the videodeck housing part 84 can be displayed on the large screen of the boardpart 81. In addition, information displayed on the screen can be printedout on sheets of paper from a printer housed in the printer housing part85.

Since information written to the screen of the board part 81 is managedby the page by letting one screen be one page, it is easy to display alist of all the pages of information displayed on the screen, torearrange pages, or to make an edition such as deletion or addition ofpages. It is also possible to store the created pages as files.

Therefore, the multimedia board 80 serves as a very convenient tool fora conference, meeting or presentation. The keyboard may be connected tothe computer to utilize the board part 81 as a conventional displayscreen of the computer so that the board part 81 can be used forproviding instructions on a computer operation.

According to this embodiment, the flat panel 81 a of the board part 81is also used as the touch panel. However, a touch panel made of atransparent material may be provided on the flat panel 81 a to serve asthe touch panel of the coordinate input and detection device.

The present invention is not limited to the specifically disclosedembodiments, but variations and modifications may be made withoutdeparting from the scope of the present invention.

The present application is based on Japanese priority application No.2000-096991 filed on Mar. 31, 2000, the entire contents of which arehereby incorporated by reference.

What is claimed is:
 1. A coordinate input and detection devicecomprising: a touch panel including a surface; a plurality of lightemitting units projecting light beams traveling parallel to the surfaceof said touch panel over a predetermined region of said touch panel,each of the light beams being a parallel beam having a uniform thicknessin a direction perpendicular to the surface of said touch panel andhaving a sector shape in a direction parallel to the surface of saidtouch panel; a reflective member provided on a peripheral portion ofsaid touch panel to reflect the light beams toward first optical pathsthrough which the respective light beams travel to reach said reflectivemember; a plurality of intensity distribution detection units receivingthe respective light beams reflected by said reflective member to detectintensity distributions of the light beams; a coordinate detection unitdetecting a coordinate value of a position where the light beams areinterrupted based on the intensity distributions; and a plurality offilters disposed in respective second optical paths in directionsperpendicular to directions in which the respective light beams travel,the second optical paths being optical paths through which therespective light beams reflected by said reflective member travel toreach said respective intensity distribution detection units, saidfilters having transmission rates varying with respect to positionswithin said filters.
 2. The coordinate input and detection device asclaimed in claim 1, wherein each of said filters has wedge-like notchesprotruding from respective end portions thereof toward a center portionthereof in a direction perpendicular to a direction of the thickness ofeach of the light beams.
 3. The coordinate input and detection device asclaimed in claim 1, wherein each of said filters is a combination of aplurality of filters having different transmission rates.
 4. Thecoordinate input and detection device as claimed in claim 1, whereineach of said filters is a combination of a plurality of filters havingdifferent shapes.
 5. The coordinate input and detection device asclaimed in claim 1, wherein each of said filters is made of a resinfilm.
 6. The coordinate input and detection device as claimed in claim1, wherein each of said filters is disposed in any position in each ofthe second optical paths to adjust an amount of light received by thelight receiving surface.
 7. An information display and input apparatuscomprising: an information display unit including a display fordisplaying a variety of information; and a coordinate input anddetection device, the device comprising: a touch panel including asurface, the touch panel serving as the display of said informationdisplay unit; a plurality of light emitting units projecting light beamstraveling parallel to the surface of said touch panel over apredetermined region of said touch panel, each of the light beams beinga parallel beam having a uniform thickness in a direction perpendicularto the surface of said touch panel and having a sector shape in adirection parallel to the surface of said touch panel; a reflectivemember provided on a peripheral portion of said touch panel to reflectthe light beams toward first optical paths through which the light beamstravel to reach said reflective member; a plurality of intensitydistribution detection units receiving the respective light beamsreflected by said reflective member to detect intensity distributions ofthe light beams; a coordinate detection unit detecting a coordinatevalue of a position where the light beams are interrupted based on theintensity distributions; and a plurality of filters disposed inrespective second optical paths in directions perpendicular todirections in which the respective lights beams travel, the secondoptical paths being optical paths through which the respective lightbeams reflected by said reflective member travel to reach saidrespective intensity distribution detection units, said filters havingtransmission rates varying with respect to positions within saidfilters.
 8. An information display and input apparatus comprising: aninformation display unit including a display for displaying a variety ofinformation; and a coordinate input and detection device, the devicecomprising: a touch panel including a surface, the touch panel beingmade of a transparent material and placed on the display of saidinformation display unit; a plurality of light emitting units projectinglight beams traveling parallel to the surface of said touch panel over apredetermined region of said touch panel, each of the light beams beinga parallel beam having a uniform thickness in a direction perpendicularto the surface of said touch panel and having a sector shape in adirection parallel to the surface of said touch panel; a reflectivemember provided on a peripheral portion of said touch panel to reflectthe light beams toward first optical paths through which the light beamstravel to reach said reflective member; a plurality of intensitydistribution detection units receiving the respective light beamsreflected by said reflective member to detect intensity distributions ofthe light beams; a coordinate detection unit detecting a coordinatevalue of a position where the light beams are interrupted based on theintensity distributions; and a plurality of filters disposed inrespective second optical paths in directions perpendicular todirections in which the respective lights beams travel, the secondoptical paths being optical paths through which the respective lightbeams reflected by said reflective member travel to reach saidrespective intensity distribution detection units, said filters havingtransmission rates varying with respect to positions within saidfilters.
 9. A coordinate input and detection device comprising: a touchpanel including a surface; a plurality of light emitting means forprojecting light beams traveling parallel to the surface of said touchpanel over a predetermined region of said touch panel, each of the lightbeams being a parallel beam having a uniform thickness in a directionperpendicular to the surface of said touch panel and having a sectorshape in a direction parallel to the surface of said touch panel;reflective means provided on a peripheral portion of said touch panelfor reflecting the light beams toward first optical paths through whichthe respective light beams travel to reach said reflective means; aplurality of intensity distribution detection means for receiving therespective light beams reflected by said reflective means to detectintensity distributions of the light beams; a coordinate detection meansfor detecting a coordinate value of a position where the light beams areinterrupted based on the intensity distributions; and a plurality offilter means disposed in respective second optical paths in directionsperpendicular to directions in which the respective light beams travel,the second optical paths being optical paths through which therespective light beams reflected by said reflective means travel toreach said respective intensity distribution detection means, saidfilter means having transmission rates varying with respect to positionswithin said filter means.